This invention relates to an improved self-aligned insulated gate field effect transistor (IGFET) and method for fabricating that device.
Self-alignment techniques are used routinely in silicon technology. These self-aligned IGFETs have reduced source and drain resistance over the non-self-aligned structures, resulting in improved performance. Examples are shown in U.S. Pat. No. by Dennard, 4,182,636 and by Lund et al, U.S. Pat. No. 4,319,395.
There is a need for ultrahigh speed electronic devices, in fields such as airborne radar and communication systems. It is anticipated that GaAs IGFETs will become an important part of these systems. Meiners U.S. Pat. No. 4,268,844 discloses an IGFET capable of operation at frequencies in excess of one GHz. The transistor substrate is a semi-insulating semiconductor which may be formed of Cr-doped GaAs, Tsang U.S. Pat. No. 4,291,327 forms IGFETs by growing a layer of controlled thickness on GaAs. Hughes et al U.S. Pat. No. 4,325,073 and Casey, Jr., U.S. Pat. No. 4,160,261 both disclose method of forming GaAs FETs.
The use of GaAs IGFETs with large interface state densities is described in my copending U.S. patent application Ser. No. 271,754 filed June 9, 1981, now U.S. Pat. No. 4,438,351 issued Mar. 20, 1984.